1. Field of the Invention
This invention relates to an LED display apparatus that displays images of pictures, letters, etc. in space utilizing a human eye's afterimage effect as the apparatus is held by an operator's hand and moved with a right and left reciprocating lotion.
2. Description of the Prior Art
A conventional LED display apparatus that utilizes an afterimage effect has consisted of, as shown in FIG. 13, batteries 31 as a power source, a power source switch 32, an array of LEDs 33 mounted on the apparatus body base and a series of timer circuits 34 that turn the LEDs 33 on or off in sequence according to a preprogrammed timing.
How the foregoing LED display apparatus operates is explained in the following:
First, the power source switch 32 is turned on and then each LED of the LED array is turned on, as shown in FIG. 14, for a fixed period T.sub.Y per respective timing program by means of the timer circuits 34 and also for a fixed repeating period T.sub.X that corresponds to one cycle of picture or letter signals. While such an operation is taking place, the LED array is moved with a right and left reciprocating motion and then images of pictures, letters, etc. are made visible in space by an afterimage effect from only one direction as shown in FIG. 15.
However, in this conventional set-up the LED array mounted on the apparatus body base is moved in a reciprocating motion on a plane situated in parallel with the plane that is inclusive of the LED array. Since the LED array has only one light emitting plane, images of pictures, letters, etc. are seen regretfully only from one direction of the front side of the apparatus body. Also, since the LEDs are turned on and off at a fixed interval of time T.sub.X irrespective of the speed of the LED array's right and left reciprocating motion, there exists no synchronization between the LED array motion and the LED's light emission resulting in an unstable formation of images with their positions varied over the range of the right and left reciprocating motion.
In addition, since each LED is turned on only for a fixed period of T.sub.Y, images of pictures, letters, etc. tend to look larger by moving the LED display apparatus faster and tend to look smaller by moving the LED display apparatus more slowly.
Furthermore, since the turn on and off sequential order of LEDs is fixed to start from one direction only, the displayed images of asymmetrical pictures, letters, etc. are reversed on the return movement of the apparatus, as shown in FIG. 16 (a) and (b), making it difficult to distinguish the images and consequently imposing a limitation in the image display capability to displaying symmetrical patterns only.